Found this info interesting. Google has a password system (authentication and authorization) which is named Gaia. This is responsible for controlling the access of google web services by millions of users worldwide. It is considered as one of the Google's crown jewels. However, this was the core component that was attacked by Chinese intruders during Jan 2010. You can find more info here.

http://www.nytimes.com/2010/04/20/technology/20google.html